The disclosure of Japanese Patent Application No. 2000-358181 filed on Nov. 24, 2000, including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The present invention relates to in-cylinder-injection internal combustion engines of the spark ignition type, and to methods of controlling such internal combustion engines.
2. Description of Related Art
JP-A-2000-80942 discloses an in-cylinder-injection internal combustion engine which has a fuel injector valve for each of its cylinders and which is started with a partial operation of a selected one or more of the cylinders with fuel injection into only the selected cylinder or cylinders, for reducing a total amount of an unburned fuel discharged from the cylinders. In this in-cylinder-injection internal combustion engine of spark ignition type, the high pressurized fuel supplied from a fuel accumulator is injected through the fuel injector valve into each cylinder in the latter half or a relatively terminal portion of the compression stroke, in which the pressure within the cylinder is relatively high.
After the engine is started in the manner described above, a pressurizing pump used to pressurize the fuel within the fuel accumulator can be operated by the started engine with a comparatively high degree of stability, so that the fuel within the fuel accumulator can be suitably pressurized so as to permit the fuel injection into the cylinders in their compression stroke. Accordingly, a full operation of the engine with the fuel injection into all of the cylinders can be subsequently performed, with stratified charge combustion which is advantageous for reducing the amount of consumption of the fuel.
In the selected cylinder or cylinders in which uniform charge combustion is effected for starting the engine, a portion of the fuel injected therein in the intake stroke remains on the cylinder bore surface and/or the top surface of the piston. Upon initiation of the full operation of the engine with the fuel injection into all of the cylinders, a part of the fuel remaining on the cylinder and/or piston surface or surfaces evaporates to form a very fuel-lean air-fuel mixture in the peripheral portion of the cylinder. Although a portion of the combustible air-fuel mixture in the vicinity of a spark plug can be comparatively well ignited, a flame produced by the ignition does not propagate to the fuel-lean air-fuel mixture in the peripheral portion of the cylinder. As a result, this fuel-lean air-fuel mixture is discharged out of the cylinder, undesirably causing a considerable increase of the amount of the unburned fuel to be discharged from the cylinder.
In the other or non-selected cylinder or cylinders not supplied with the fuel during the partial engine operation with the fuel injection into the selected cylinder or cylinders, the air-fuel mixture can be ignited with high stability, with the stratified charge combustion, in the subsequent full engine operation with the fuel injection into all of the cylinders. On the other hand, however, the non-selected cylinder or cylinders tends/tend to produce a comparatively large amount of smoke due to incomplete combustion since the temperature in the non-selected cylinder or cylinders is lower than that in the selected cylinder or cylinders. Thus, the overall exhaust emission of the engine is deteriorated when the full engine operation is initiated following the partial engine operation with the fuel injection into only the selected cylinder or cylinders.
It is therefore an object of the present invention to improve an exhaust emission produced by an in-cylinder-injection internal combustion engine of spark ignition type upon initiation of a full operation of the engine with fuel injection into all of its cylinders after fuel pressure within a fuel accumulator is raised to a level permitting the fuel injection into each cylinder in the compression stroke, as a result of a partial engine operation with the fuel injection into only a selected one or more of the cylinders, and to reduce the amount of consumption of the fuel in the full operation of the engine.
According to a first aspect of this invention, there is provided an in-cylinder-internal internal combustion engine of spark ignition type which has a plurality of cylinders and which is started by a partial operation of a selected at least one of the cylinders with a fuel injected into the selected at least one of the cylinders in at least its intake stroke. The partial operation is followed by a full operation of all of the cylinders with the fuel injected into all of the cylinders. The full operation is initiated when or after (i.e., not before) a pressure of the fuel in a fuel accumulator has been raised to a level high enough to permit injection of the fuel into each of the cylinders in its compression stroke, as a result of the partial operation of the selected at least one of the cylinders. In addition, an initial portion of the full operation of all of the cylinders includes a first mode of combustion in the selected at least one of the cylinders with the fuel injected thereinto in at least its intake stroke, the first mode of combustion being followed by stratified charge combustion in the selected at least one of the cylinders with the fuel injected thereinto in only the compression stroke.
According to a second aspect of the invention, there is provided an in-cylinder-injection internal combustion engine of spark ignition type which has a plurality of cylinders and which is started by a partial operation of a selected at least one of the cylinders with a fuel injected into the selected at least one of the cylinders in at least its intake stroke. The partial operation is followed by a full operation of all of the cylinders with the fuel injected into all of the cylinders. The full operation is initiated when or after (i.e., not before) a pressure of the fuel in a fuel accumulator has been raised to a level high enough to permit injection of the fuel into each of the cylinders in its compression stroke, as a result of the partial operation of the selected at least one of the cylinders. In addition, an initial portion of the full operation of all of the cylinders includes a first mode of combustion in each of the other of the plurality of cylinders (i.e., each of the cylinders other than the selected cylinder(s)) with the fuel injected thereinto in at least its intake stroke, the first mode of combustion being followed by stratified charge combustion in each of the other cylinder(s) with the fuel injected thereinto in only its compression stroke.
According to a third aspect of the present invention, there is provided an in-cylinder-injection internal combustion engine of spark ignition type which has a plurality of cylinders and which is started by a partial operation of a selected at least one of the cylinders with a fuel injected into the selected at least one of the cylinders in at least its intake stroke. The partial operation is followed by a full operation of all of the cylinders with the fuel injected into all of the cylinders. The full operation is initiated when or after (i.e., not before) a pressure of the fuel in an accumulator has been raised to a level high enough to permit injection of the fuel into each of the cylinders in its compression stroke, as a result of the partial operation of the selected at least one of the cylinders. In addition, an initial portion of the full operation of all of the cylinders includes a first mode of combustion with the fuel injected into full of the cylinders in at least its intake stroke, the first mode of combustion being followed by stratified charge combustion with the fuel injected into full of the cylinders in only its compression stroke, and furthermore, the stratified charge combustion in the selected at least one of the cylinders is initiated before that in each of the other cylinder(s).
According to a fourth aspect of this invention, there is provided a method of controlling an in-cylinder-injection internal combustion engine of spark ignition type having a plurality of cylinders, comprising: a step of starting the engine by a partial operation of a selected at least one of the plurality of cylinders with a fuel injected into the selected cylinder(s) in at least its intake stroke; a step of initiating a full operation of all of the cylinders with the fuel injected into all of the cylinders, when or after (i.e., not before) a pressure of the fuel in a fuel accumulator has been raised to a level high enough to permit injection of the fuel into each of the cylinders in its compression stroke, as a result of the partial operation of the selected cylinder(s); and a step of controlling the full operation of all of the cylinders such that an initial portion of the full operation includes a first mode of combustion in the selected cylinder(s) with the fuel injected thereinto in at least its intake stroke, the first mode of combustion being followed by stratified charge combustion in the selected cylinder(s) with the fuel injected thereinto in only the compression stroke.
According to a fifth aspect of this invention, there is provided a method of controlling an in-cylinder-injection internal combustion engine of spark ignition type having a plurality of cylinders, comprising: a step of starting the engine by a partial operation of a selected at least one of the cylinders with a fuel injected into the selected cylinder(s) in at least its intake stroke; a step of initiating a full operation of all of the cylinders with the fuel injected into all of the cylinders, when or after (i.e., not before) a pressure of the fuel in a fuel accumulator has been raised to a level high enough to permit injection of the fuel into each of the cylinders in its compression stroke, as a result of the partial operation of the selected cylinder(s); and a step of controlling the full operation of all of the cylinders such that an initial portion of the full operation includes a first mode of combustion in each of the other of the plurality of cylinders (i.e., the non-selected cylinder or cylinders) with the fuel injected thereinto in at least its intake stroke, the first mode of combustion being followed by stratified charge combustion in each of the other cylinder(s) with the fuel injected thereinto in only its compression stroke.
According to a sixth aspect of this invention, there is provided a method of controlling an in-cylinder-injection internal combustion engine of spark ignition type having a plurality of cylinders, comprising: a step of starting the engine by a partial operation of a selected at least one of the cylinders with a fuel injected into the selected cylinder(s) in at least its intake stroke; a step of initiating a full operation of all of the cylinders with the fuel injected into all of the cylinders, which full operation is initiated when or after (i.e., not before) a pressure of the fuel in a fuel accumulator has been raised to a level high enough to permit injection of the fuel into each of the cylinders in its compression stroke, as a result of the partial operation of the selected cylinder(s); and a step of controlling the full operation of all of the cylinders such that an initial portion of the full operation includes a first mode of combustion with the fuel injected into full of the cylinders in at least its intake stroke, the first mode of combustion being followed by stratified charge combustion with the fuel injected into full of the cylinders in only its compression stroke, wherein the stratified charge combustion in the selected cylinder(s) is initiated earlier than in each of the other (i.e., the non-selected) cylinder(s).